Exposure to hot and cold environmental conditions does not affect the decision making ability of soccer referees following an intermittent sprint protocol.

mm m

PHYSIOLOGY

ORIGINAL RESEARCH ARTICLE

published: 20 May 2014
doi: 10.3389/fphys.2014. 00185

Exposure to hot and cold environmental conditions does
not affect the decision nnaking ability of soccer referees
following an internnittent sprint protocol

Lee Taylor^*, Natalie Fitch\ Paul Castle\ Samuel Watkins^ Jeffrey Aldous \ Nicholas Sculthorpe^,
Adrian Midgely^, John Brewer^ and Alexis Mauger*

' Sport Science and Physical Activity, Sport and Exercise Science Laboratory, University of Bedfordsliire, Bedford, UK

' School of Science, University of West Scotland, Hamilton, Scotland

^ Department of Sport and Physical Activity, Edge Hill University, Ormskirk, UK

" School of Sport and Exercise Sciences, University of Kent, Chatham Maritime, UK

Soccer referees enforce the laws of the game and the decisions they mal<e can
directly affect match results. Fixtures within European competitions take place in climatic
conditions that are often challenging (e.g., Moscow ~ -5°C, Madrid ~30°C). Effects of
these temperatures on player performance are well-documented; however, little is known
how this environmental stress may impair cognitive performance of soccer referees and
if so, whether exercise exasperates this. The present study aims to investigate the
effect of cold [COLD; -5°C, 40% relative humidity (RH)], hot (HOT; 30°C, 40% RH)
and temperate (CONT; 18°C, 40% RH) conditions on decision making during soccer
specific exercise. On separate occasions within each condition, 13 physically active
males; either semi-professional referees or semi-professional soccer players completed
three 90min intermittent treadmill protocols that simulated match play, interspersed
with 4 computer delivered cognitive tests to measure vigilance and dual task capacity.
Core and skin temperature, heart rate, rating of perceived exertion (RPE) and thermal
sensation (TS) were recorded throughout the protocol. There was no significant difference
between conditions for decision making in either the dual task (interaction effects: FALSE
p = 0.46; MISSED p = 0.72; TRACKING p = 0.22) or vigilance assessments (interaction
effects: FALSE p= 0.31; HIT p = 0.15; MISSED p = 0.17) despite significant differences
in measured physiological variables (skin temperature: HOT vs. CONT 95% CI = 2.6 to 3.9,
p < 0.001 ; HOT vs. COLD 95% CI = 6.6 to 9.0, p < 0.001 ; CONT vs. COLD 95% CI = 3.4
to 5.7 P < 0.01 ). It is hypothesized that the lack of difference observed in decision making
ability between conditions was due to the exercise protocol used, as it may not have
elicited an appropriate and valid soccer specific internal load to alter cognitive functioning.

Keywords: soccer referee, thermoregulation, cognition, hot, cold

Edited by:

Martin Buchheit, Aspire, Academy
For Sport Excellence, Qatar

Reviewed by:

Martin Buchheit, Aspire, Academy
For Sport Excellence, Qatar
Naoto Fujii, University of Ottawa,
Canada

Julien Periard, ASPETAR - Qatar
Orthopaedic and Sports Medicine
Hospital, Qatar

*Conespondence:

Lee Taylor, University of
Bedfordshire, Polhlll Campus,
Polhill Avenue, Bedford,
Bedfordshire MK41 9EA, UK
e-mail: lee.taylor@beds.ac.uk

INTRODUCTION

Soccer is considered the most popular sport in the world (Reilly,
1997), with elite competitive matches requiring an officiating
team [referee, assistants x 2 and within the Union of European
Football Associations (UEFA) region 2 x goal line officials] to
apply the laws of the game (Castagna et al., 2007). Football is char-
acterized by variable intermittent activity and recovery, inherently
displaying more complex physiological requirements than sports
with continuous exercise (Drust et al, 2000). The physiological
demands of refereeing are similar to that of a midfield soc-
cer player, with total distance covered and high speed running
consistent between player and referee (Weston et al., 201 1).

Increased physical fatigue in a referee can elicit an inability to
maintain proximity to key incidents within game play (varying
rule infringements), with increases in the infringement/distance
nexus, known to impair decision making ability (Catterall et al,
1993). Therefore, repeated sprint ability is of high importance
for referees to maintain proximity to such incidents (Galanti

et al., 2008). Compounding issues regarding proximity, high
intensity exercise per se is known to have negative effects on
cognition (McMorris and Graydon, 1997), with such cognitive
decrements associated with altered arousal and narrowed atten-
tion (Brisswalter et al, 2002). Thus, the interplay between the
physical demands of refereeing and decision making is important,
yet, requires further elucidation.

The UEFA Champions League and The UEFA Europa
League, played principally in Europe between September and
May, ensures referees often perform their roles within vary-
ing challenging environmental conditions [Madrid (~30°C) and
Moscow (~ -5°C)] within the UEFA region and season. Indeed,
intermittent sprint exercise in hot conditions (exercise-heat
stress) is known to increase thermoregulatory and physiological
strain/load (Duffield et al., 2009), reducing physiological perfor-
mance (i.e., distance covered), and likely further disturbs arousal
levels (Bandelow et al., 2010), when compared to similar exer-
cise in temperate conditions. Conversely, cold temperatures can

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Taylor et al.

The environment and soccer referee decision mal<ing

cause severe discomfort and lead to a drop in body temperature
(Parsons, 2003), which, may also effect cognitive performance due
to distraction (Makinen et al, 2006). However, metabolic heat
production during soccer specific exercise may help overcome the
distraction and severe discomfort associated with cold temper-
atures (Brotherhood, 2008), although, whether this ameliorates
the well-reported negative effects on cognitive function (Makinen
et al, 2006; Racinais et al., 2008) has yet to be confirmed. Despite
evidence that both heat (Racinais et al., 2008; Simmons et al,
2008) and cold stress (Makinen et al., 2006) detrimentally effect
cognitive capacity and performance, this has not been studied
in soccer referees, who are constantly required to make correct
decisions on infringements and are regularly exposed to envi-
ronmental extremes within the UEFA region and season, whilst,
performing soccer specific exercise. Referee decisions can often
affect the outcome of a match and thus it is important to under-
stand the interaction between the ambient environment and the
ability of soccer referees to make correct decisions.

Due to inherent difficulties, and likely confounding nature
in the inability to standardize the external environment (both
weather and games factors players, tactics, results, etc.) and
physiological demands within an actual match the tripartite
research questions of interest here (decision making, physiolog-
ical demands/capacity and environmental fluctuations) would be
best explored by a treadmill based, environmental chamber deliv-
ered protocol. The seminal work of Drust et al. (2000) is currently
the most used protocol and will be utilized within the present
study.

The aims of the present study were to investigate the effect of
hot and cold conditions, typical of the UEFA region and season,
on decision making and physiological responses of soccer refer-
ees during a treadmill based intermittent sprint protocol (Drust
et al, 2000). It was hypothesized that hot temperatures would
increase the fatigue that is associated with the exercise protocol
and thus cause a detrimental effect on decision making. Cold con-
ditions would have no significant effect on core temperature, but
skin temperature (Tsk) would significantly decrease, resulting in a
negligible effect on decision making ability.

METHODS

SUBJECTS AND GENERAL EXPERIMENTAL CONTROLS

Thirteen physically active males; either semi-professional refer-
ees (« = 7) or semi-professional soccer players (m = 6) (mean ±
SD: age = 20.3 ± 2.2 years; height = 175 ± 7.4 cm; body
mass = 70.8 ± 4 kg) volunteered for this study. Sample size of
12 was calculated using computer software (G*Power 3), and
was deemed sufficient to observe significant differences in the
dependant variable rectal temperature (Tre) based on the pre-
vious findings (Drust et al., 2000). All participants were fuUy
informed of the risks associated with this study before they gave
fuU written consent to take part in testing. The procedures were
approved by the University of Bedfordshire Ethics Committee.
All participants abstained from alcohol, cigarettes, caffeine and
strenuous exercise at least 48 h prior to testing and maintained
their normal diet prior to and during the testing sessions (in line
with; Taylor et al, 2012). Additionally, all participants refrained
from supplementation of ergogenic aids throughout the study

and abstained from exposure to extreme hot or cold conditions
7 d prior to testing (in line with; Taylor et al., 2012). Adherence
was assessed by questionnaire, with no violations seen for these
control parameters.

A urine refractometer (Alago Vitech Sicentific, Pocket PAL-
OSMO, West Sussex, UK) was used to measure the hydration
levels of the participants on arrival of each visit. Participants
were asked to consume ~5-7ml kg^' of water 2-3 h before
each experimental visit, in line with previous recommendations
(Sawka et al, 2007). A participant was deemed to be euhydrated
if urine osmolarity was < 600 mOsm-Kg^' H2O as previously
used (Hillman et al., 2011), this control was not violated for any
experimental procedure or exercise bout.

PROCEDURES

Participants reported to the laboratory on five occasions. The
first two were to collect anthropometric data and for familiar-
ization to the intermittent sprint exercise protocol (Drust et al,
2000) and cognitive tests (Hope et al., 1998). Visit 1 consisted of
familiarization to the cognitive software, where as visit 2 included
familiarization to both the cognitive software and the intermittent
sprint protocol. For the remaining three visits, which were each
separated by 7 d, participants completed the protocol in a ran-
domized order inside an environmental chamber in either a cold
condition [COLD; -5°C; 50% relative humidity (RH)], temper-
ate control condition (CONT; 18° C; 50% RH) or hot condition
(HOT; 30° C; 50% RH).

VISIT 1

Anthropometric data and familiarization

Upon arrival to the laboratory, air displacement plethysmogra-
phy (BodPod, 2000A, Cranlea, Birmingham, UK) was used to
assess body composition in accordance with the manufacturers'
guidelines.

Cognitive tests. Participants sat in the environmental chamber at
a temperature of 18°C and 50% RH and performed the vigilance
(VIG) and dual task (DT) cognitive tests, using the Psyche soft-
ware package (Hope et al., 1998). To ensure all learning effects
were removed, participants were familiarized to both tests on two
occasions (Hope et al., 1998). The VIG test measured vigilance
performance which consisted of 3 digit numbers that flashed on a
screen 100 times per min. Participants were required to press the
space bar on a keyboard when they identified that the 3 digit num-
ber was duplicated (Hope et al, 1998). FALSE, HIT, and MISSED
scores were recorded (see Table 1). The DT test measures tracking
and visual reaction time. To measure tracking, participants were
required to control the screen cursor which must follow a mov-
ing blue circle on the computer screen. At random intervals, a
small icon appeared on the screen and the participant had to press
the spacebar to acknowledge the icon (Hope et al, 1998). FALSE,
MISSED, and TRACKING scores were recorded (see Table 1).
Both tests lasted for 3 min.

Exercise protocol. A warm-up, intermittent sprint protocol
and cool down were all conducted on a motorized-treadmill
(Woodway, PPS55 Med-I, Cranlea, Birmingham, UK) as a

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Taylor et al.

The environment and soccer referee decision mal<ing

Table 1 | Ecological examples of cognitive tests used.

Output

Vigilance

Dual task

Definition

Ecological example

Definition

Ecological example

FALSE

Recorded when a numerical

A referee awards a free kick

When the participant

Referee incorrectly indentifies an

duplication is incorrectly

to the attacking team when

incorrectly indicates the icon is

off the ball incident (in their field

acknowledged.

the attacking player has dived.

present when it is not.

of vision), whilst concentrating on

trie uail.

MISSED

Recorded when a numerical

A referee fails to spot an

When the participant fails to

Referee fails to spot an off the

duplication is missed.

infringement e.g., a player is

indicate the presence of the

ball incident which has taken

fouled but no free kick

icon.

place close to the ball (in their

awarded.

field of vision).

HIT

Recorded when a numerical

When a referee correctly

N/A

N/A

duplication is correctly identified.

indentifies an infringement

and a free kick is awarded.

TRACKING

N/A

N/A

The participant's ability to track

Referees ability to track the ball

a moving target around the

e.g., a corner is taken and the ball

screen with the mouse cursor.

enters the penalty area and has

its trajectory diverted quickly.

familiarization to the exercise protocol. Participants completed a
5 min warm up which consisted of jogging at a speed of 10 km.h^'
at 1% gradient. They then completed 45 min of the intermittent
exercise protocol (Drust et al, 2000) to experience the changes of
intensities and general requirements of successful protocol com-
pletion. The fuU 90 min protocol (Drust et al., 2000) was not
used for familiarization due to both halves using the same move-
ment patterns. Core temperature (rectal temperature) and Tsk
were recorded during familiarization in order for participants to
experience the full data collection process. This was completed in
temperate conditions (18°C, 40% RH).

The intermittent sprint exercise protocol

A 105 min protocol including 90 min of exercise (composed of
2 X 45 min halves of intermittent exercise, interspersed with a
15 min rest period) was utilized (Drust et al., 2000), which,
replicated the movement patterns and thus physiological loads
experienced by referees during a football match (Figure 1). As
professional referee movement patterns are similar to those of
a soccer midfielder (Weston et al, 2011) the use of a protocol
designed to mimic the movement patterns of an outfield player
is justified. A timeline of the protocol is shown in Figure 1.

The 90 min of exercise consisted of 5 movements that are
observed during a match. These include standing, walking, jog-
ging, running and sprinting. The duration and speeds are shown
in Table 2.

The varying speeds were randomly assigned to different time
points of the 90 min protocol i.e., varying speeds were randomly
assigned throughout the master protocol which was used for all
subjects in all conditions.

EXPERIMENTAL DESIGN

Participants were asked to wear t-shirt and shorts for testing
conditions, in line with referee's attire during a match.

Once hydration status had been assessed, a heart rate (HR)
monitor (Polar, FSl, Cranlea, Birmingham, UK) was attached
to the chest. A rectal thermistor (Henleys, 400H and 4491H,

Henleys, Herts, UK) inserted 10 cm past the anal sphincter was
used to measure Tre, with Tre recorded via a temperature moni-
tor (Libra Medical, ET402, Cranlea, Birmingham, UK). Tsk was
assessed using skin thermistors (Grant, EUS-U-VS5-0, Wessex
Power, Dorset, UK) which were placed on the pectoral, tricep,
gastrocnemius and vastus lateralis of the right side of the body
(Ramanathan, 1964) using general medical tape. Once aU ther-
mistors were attached, they were connected to a data logger
to record T^k (Squirrel 451, Grant instruments, Wessex Power
UK). Mean T^k was calculated using the following equation
(Ramanathan, 1964):

Mean Skin Temperature (Tsk) : O.STchest + O.STarni

+0.2rthigh + 0.2rcaif

Once all baseline measurements were recorded (Figure 1), partic-
ipants entered the environmental chamber to perform the first
set of cognitive tests. Once completed, participants performed
a 5 min warm up on the treadmill at a speed of lOkm.h^' at
1% gradient, followed by the first half of the exercise protocol.
The second cognitive test was performed immediately after the
first half (Figure 1) in the environmental chamber. Participants
moved from the chamber into a temperate environment for
the 15 min rest period (Figure 1). The third cognitive test was
performed after the 15 min rest period, immediately before the
second half (Figure 1) in the environmental chamber. The final
cognitive test was completed immediately after the second half
(Figure 1) in the environmental chamber.

HR, Tre, Tsk, rating of perceived exertion (RPE) (Borg, 1970)
and thermal sensation (TS) (Toner et al., 1986) were recorded at
rest and every 5 min throughout the experimental protocol.

STATISTICAL ANALYSIS

Statistical analysis was conducted using IBM Statistical Package
for Social Science (SPSS) (version 19). Statistical assump-
tions were checked using conventional graphic methods and

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Taylor et al.

The environment and soccer referee decision mal<ing

Baseline Measures (Height, Body Mass)
Cognitive Tests (Omin) (Chamber)
45 min exposure to environment (1" Half) (Chamber)
Cognitive Tests on completion of 1" Half (Chamber)
15 min Half time break (Outside Chamber 18 °C)
Cognitive Tests on completion half time break (Chamber)
45 min exposure to environment (2"'' Half) (Chamber)
Cognitive Tests on completion of 2"'' Half (Chamber)

FIGURE 1 I Schematic of the 90 min experimental procedure which was carried out in all 3 conditions.

Table 2 | Speed and durations of the 5 different movements during
the 90 min intermittent sprint exercise protocol.

Movement

Speed (km.h~^)

Duration (s)

Movements in half

Stand

0

60

7

Walk

6

120

7

Jog

12

57

19

Run

15

33

8

Sprint

20

6

6

were deemed plausible in all instances. Central tendency and
dispersion are reported as the mean (± SD). All data from
the main experimental trials were analyzed using a Two-Way
repeated measures (condition x time) AN OVA. Bonferroni post-
hoc comparisons were used to identify specific differences across
time between changes. Two-tailed significance was accepted as
P < 0.05.

RESULTS

PHYSIOLOGICAL MEASURES
Rectal temperature

A significant main effect for condition (_F = 3.7, p = 0.039) was
observed for Tre (Figure 2A), where mean T^e was 0.28° C lower in
COLD than CONT (95% CI = 0.11 to 0.58,p = 0.041), however,
there were no significant differences observed between CONT
and HOT (mean difference = 0.20°C, 95% CI = -0.12 to 0.51,
p = 0.34) or COLD and HOT (mean difference = 0.09° C, 95%
CI = -0.21 to 0.38, p = 1.00). A significant interaction effect
(_F = 3A,p < 0.001) showed that changes in Tre across time were
not consistent across conditions, with the greatest increases in Tre
being observed in HOT and the smallest increases in COLD.

Skin temperature

There was a significant main effect for condition (F = 217.5, p <
0.001), where mean Tsk was 3.3°C higher in HOT than in CONT
(95% CI = 2.6 to 3.9, p < 0.001) and 7.8°C higher than in COLD
(95% CI = 6.6 to 9.0, p < 0.001), and 4.5°C higher in CONT
than in COLD (95% CI = 3.4 to 5.7, p < 0.001) (Figure 2B).
A significant interaction effect also was observed (_F = 18.6, p <
0.001), where T^k in CONT remained relatively stable during the
90 min, whereas in COLD there was a 5°C reduction and in HOT
there was a 3°C increase.

Heart rate

A significant main effect was observed for condition {F = 11.0,
p < 0.001), where mean HR was 13bpm higher in HOT than
in COLD (95% CI = 7 to 19, p < 0.001), however, no signifi-
cant differences were observed between HOT and CONT (mean
difference = 5bpm, 95% CI = -3 to 12, p = 0.32), or COLD
and CONT (mean difference = 8bpm, 95% C7 = -1 to 18,p =
0.087) (Figure 2C). A significant interaction effect showed that
the increase in HR over the 90 min was 16bpm greater in HOT
compared to COLD and CONT (F = 2.1,p < 0.001; Figure 2C).

SUBJECTIVE MEASURES
Thermal sensation (TS)

A significant main effect was observed for condition (F = 33.9,
p < 0.001), where mean TS was 2.4 units higher in HOT than in
COLD (95% CI = 1.4 to 3.4, p < 0.001) and 1.7 units higher in
CONT than in COLD (95% CI = 1.0 to 2.3, p < 0.001), but there
were no significant difference between HOT and CONT (mean
difference = 0.8, 95% CI = -0.1 to 1.6, p = 0.10). A significant
interaction effect showed that the change in TS over the 90 min
was different in the three conditions — 1.8, -0.4, and 3.0 units

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The environment and soccer referee decision mal<ing

39.0

38.5

Hi

3

38 0

d»

itemi

37.5

o
o

37.0

36.5

B

36

34

32

«

30

emf

28

c

CO

26

24

-0- Control

-O Hot

-O Cold

in CONT, COLD, and HOT, respectively, {F ■-
(Figure 2D).

9.1, p < 0.001)

0 5 10 15 20 25 30 35 40 45 HT 50 55 60 65 70 75 80 85 9
Time (min)

Rating of perceived exertion

There was a significant main efl^ect for condition (F = 12.0, p <
0.001), where mean RPE was 1.7 units higher in HOT than in
COLD (95% CI = 0.5 to 3.0, p = 0.006) and 1.4 units higher than
in CONT (95% CI = 0.2 to 2.6, p = 0.025), but no significant
difference between CONT and COLD (mean difference = 0.4,
95% CI = -0.1 to 0.9, p = 0.20). A significant interaction effect
showed that the increase in RPE across the 90 min was different
across conditions, with mean increases of 6, 7, and 9 units for
the COLD, CONT, and HOT conditions, respectively (_F = 3.2,
p < 0.001) (Figure 2E).

COGNITIVE PERFORMANCE
Dual tasl(

There were no significant main effect for condition (_F = 0.2, p =
0.79), time (_F = 1.9, p = 0.15), or an interaction effect between
condition and time {F = l.O,p = 0.46) observed in FALSE scores
(Figure 3A).

There was no statistically significant main effects of condition
(F = 0.2, p = 0.81) and time (_F = 0.8, p = 0.52), or condition x
time interaction (_F = 0.6, p = 0.72) observed for MISSED scores
(Figure 3B).

For TRACKING scores, there were no statistically significant
main effects of condition (_F = 1.9, p = 0.18) and time {F = 0.8,
p = 0.49), or condition x time interaction {F = 1.4, p = 0.22)
observed (Figure 3C).

Vigilance

There were no statistically significant main effects of condition
{F = 1.5, p = 0.24) and time (_F =2.l,p = 0.11), or condition x
time interaction (_F = 1.2, p = 0.31) observed for FALSE scores
(Figure 3D).

There was no statistically significant main effects of condition
(F = 0.6, p = 0.54) and time (_F = 0.3, p = 0.84), or condition x
time interaction (f= 1.6, p = 0.15) observed for HITS scores
(Figure 3E).

No statistically significant main effects for MISSED scores were
observed in condition [F = 0.5, p = 0.63) and time {F = 0.2,
p = 0.92), or condition x time interaction (_F = 1.6, p = 0.17;
Figure 3F).

Since the cognitive performance effects were small and not sta-
tistically significant, mean differences and associated confidence
intervals for pairwise comparisons have been omitted; however,
an appreciation of pairwise mean differences can be obtained
from Figure 3.

FIGURE 2 I (A) Mean (SD) rectal temperature during the 90 min
intermittent sprint exercise protocol in CONT HOT and COLD conditions.
(B) Mean (SD) skin temperature during the 90 min intermittent sprint
exercise protocol in CONT HOT and COLD conditions. (C) Mean (SD) heart
rate during the 90 min intermittent sprint exercise protocol in CONT, HOT,
and COLD conditions. (D) Mean (SD) thermal sensation during the 90 min
intermittent sprint exercise protocol in CONT HOT and COLD conditions.
(E) Mean (SD) ratings of perceived exertion during the 90 min intermittent
protocol in CONT, HOT, and COLD conditions.

DISCUSSION

The aim of this investigation was to examine whether environ-
mental conditions typical of the UEFA region and season, could
have an effect on decision making and physiological responses
within participants during a soccer specific intermittent sprint
protocol (Drust et al., 2000). The main finding was that HOT
caused no detriment to decision making performance, thus
rejecting the hypothesis that heat stress would cause decrement

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Taylor et al.

The environment and soccer referee decision mal<ing

■ Cdd

Hot

TlmtfRilnulM)

g 50

mi

Time (minutes)

Ttm«(mlnul«s>

FIGURE 3 I Mean (SD) dual task scores during the 90min
intermittent sprint exercise protocol in CONT, HOT, and COLD
conditions (A) FALSE, (B) MISS, and (C) TRACKING. Mean (SD)

to referee cognitive performance. Similar results were observed
for COLD as hypothesized.

The novel finding from the present study is that thermal
challenges (HOT and COLD) do not negatively affect refer-
ees decision making ability — negative cognitive responses were
not increased during exposure to hot conditions. Moreover,
positive cognitive responses suffered no decrement during exer-
cise in the heat. Similarly, no difference in core temperature
was observed between conditions [CONT and HOT conditions
(p= 0.33); COLD and HOT conditions (p = 1.00)]. A lack
of difference in T^e between conditions may be attributable
to a number of variables; it may be that a lower resting Tre
prior to exercise in HOT may have masked any difference in
increase rate across conditions. Moreover, it may be that
the exercise protocol was not strenuous enough to induce suf-
ficient thermoregulatory strain in the hot condition. Finally, it
may be HOT was only warm conditions, again providing insuf-
ficient thermoregulatory load. However, Tsk was significantly

B <5

*\

35

3

• 25

lit

45 4S2
TjiTM(mjnul«s)

Tim* Imi miles)

vigilance scores during the 90min intermittent sprint exercise protocol
in CONT HOT and COLD conditions (D) FALSE, (E) HITS, and (F)
MISS.

higher in HOT than CONT {p < 0.001) and COLD {p <
0.001).

The absence of significant differences in cognitive performance
between conditions within the present study (see Figure 3) are
likely attributable to the lack of significant differences in T^e
observed [CONT (38.05 ± 0.08) vs. HOT (37.85 ± 0.06); p =
0.33; COLD (37.7 ± 0.09) vs. HOT (p = 1.00) (see Figure 2A)].
Exercise-heat stress induced increases in core temperature results
in a reduction in cerebral blood flow (Fu)ii et al., 2008; Brothers
et al., 2009; Hayashi et al., 2011), suppressed arousal (Nielsen
et al, 2001) and reductions in cognitive capacity (Bandelow et al,
2010). Moreover, reductions in cerebral blood flow have been
shown to correlate with exercise fatigue (Nybo and Nielsen, 2001;
Thomas and Stephane, 2008). This interplay between core body
temperature and cognitive processes (Nielsen et al, 2001; Nybo
and Nielsen, 2001; Bandelow et al., 2010), which are not signif-
icantly disturbed within the utilized experimental design (likely
due to the exercise protocol used (Drust et al., 2000), as discussed

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The environment and soccer referee decision mal<ing

later in text), may provide explanation for the lack of variance
in cognitive performance across and between conditions in the
present study.

The utilized "Drust Protocol" (Drust et al., 2000) provides an
instrument which is designed to mimic the movement patterns
(various speeds and durations of movements and associated rest
periods) of out-field soccer players. As soccer players and ref-
erees display similar types of movement (walk, jog, run, cruise
and sprint) and cover similar distances [referees 9-13 km (Reilly
and Gregson, 2006); players ~ 9-12 km (Di Salvo et al, 2013)]
over the duration of a 90 min match, the Drust Protocol (Drust
et al., 2000) was selected for the present study. This protocol is
conducted on a motorized treadmill, using fixed speeds which
are not individualized to each participant's physiological capac-
ity, e.g., peak sprint/treadmill speed. Lack of individualization in
physiological load, likely produced differential internal and exter-
nal loads within subjects. The mean average HR across conditions
in the present study (COLD: 138 ± 5; CONT: 146 ± 6; HOT: 151
± 5), compared to 165 bpm from soccer match play (Catterall
et al., 1993) and 167 bpm from an appropriately valid and reliable
treadmill based soccer simulation (Aldous et al., 2013) respec-
tively, suggests that physiological load in the present study was
not indicative, thus not valid, in light of the values typically seen
in soccer match play (Catterall et al., 1993; Castagna et al., 2007;
Krustrup et al., 2009; Bradley and Noakes, 2013). Further con-
cern is raised by the highest mean RPE recorded throughout HOT
(30°C) in the present study being 15 (HARD), whereas repeated
sprint protocols typically elicit RPE >18 (Drust et al, 2005).

Additionally, match analysis data (Reilly and Gregson, 2006)
provides commentary on the distances covered by soccer match
officials, the types of movement, and the difference in perfor-
mance between the first and second half It was reported that
soccer referees from different national leagues (English Premier
League & Danish SuperLiga) (Catterall et al, 1993; Krustrup and
Bangsbo, 2001) as well as elites soccer players (Mohr et al., 2003;
Bradley and Noakes, 2013), all covered less distance running at
high intensities and less overall distance, during the second half of
matches. As the Drust protocol utilizes fixed speeds on a motor-
ized treadmill there is no allowance for this bi-phasic performance
between halves, and thus not reflective of actual match play per-
formance in soccer referees (Catterall et al., 1993; Krustrup and
Bangsbo, 2001) or players (Mohr et al, 2003; Bradley and Noakes,
2013). The HOT condition final T,e (90 min) (38.4°C ± 0.4) was
lower than that reported in soccer match play data for both pro-
fessional soccer players (38.5°C) and recreational soccer players
(39.0°C) (90 min); even though these results were collected in
temperate conditions (16°C) (Edwards and Clark, 2006). This
lack of appropriate specific physiological load (i.e., reflective of
a referee/player during a game), could be pivotal in the lack of
cognitive impairment seen in the present study, for example the
core temperature cognition nexus previously described, which
was hypothesized to occur within HOT. As the movement pat-
terns of soccer referees and players are similar (Weston et al.,
2011) such comparisons are possible, and demonstrate that the
physiological load experienced during the Drust Protocol was not
sufficient, nor valid when compared to match play data (Mohr
et al, 2003; Barros et al., 2007; Bradley and Noakes, 2013).

A further point of interest that may explain the disparity in
continuity between the present study and that of Drust et al.
(2000) may be the difference in fitness between the two studies.
The study by Drust et al. (2000) used university standard football
players where as the present study used both semi-professional
footballer players and referees. If those participants recruited for
the present were fitter than those from Drust et al. (2000) due
to their superior level of soccer participation it may be that the
Drust protocol is valid for use on amateur soccer players but not
semi-professional/professional. In the present study there were
no significant differences in decision making ability during and
between all conditions, likely due to the validity issues outlined
above regarding the employed protocol (Drust et al., 2000).

A recently published protocol utilizing a non-motorized tread-
mill based intermittent soccer-specific performance test (iSPT)
(Aldous et al., 2013) provides the individualized variance (e.g.,
reduction in distance covered between 1st and 2nd halves)
observed in real-life match play in soccer players (Mohr et al.,
2003; Barros et al, 2007; Bradley and Noakes, 2013) and refer-
ees (Catterall et al, 1993; Krustrup and Bangsbo, 2001), which
was absent in the utilized protocol (Drust et al., 2000). Data from
the iSPT displays reductions in total distance covered and dis-
tance covered at high intensities during the second 45 min of a
90 min protocol (Aldous et al., 2013), similar to the field data
observed in elite referees (Krustrup and Bangsbo, 200 1 ; Reilly and
Gregson, 2006) and players (Mohr et al, 2003; Barros et al, 2007;
Bradley and Noakes, 2013). All variables associated with inter-
nal and external load in response to iSPT (Aldous et al., 2013),
were shown to be reliable, and valid in comparison to match play
data. Therefore, it is recommended that the present experimental
design be repeated with the protocol employed (Drust et al., 2000)
replaced with iSPT (Aldous et al, 2013), or a similar appropriately
constructed protocol (Williams et al, 2010).

The interaction between skin blood flow (Tji;) and Tre must
not be overlooked. Alterations in skin blood flow may explain
why Tre did not display noticeable change between conditions.
It is plausible that increases in skin blood flow and thus increases
in skin temperature provided sufficient thermoregulatory home-
ostasis via heat evaporation and radiation that T^e did not
increase in the hot condition — particularly if either the hot condi-
tion was not hot enough, the exercise protocol was not strenuous
enough or a combination of both. This provides explanation for
the non-significant difference in Tre between conditions as well as
the statistically significant difference in Tjk between conditions.

As hypothesized, there was no effect on cognition in the COLD
condition. Whilst performing the exercise protocol, metabolic
heat would be produced by the working muscles (Brotherhood,
2008) and this may serve to maintain deep body temperature
(Tre). Whilst maintaining Tre, there will be a decline in tempera-
ture in the peripheral tissue (Tipton, 2006), which was observed
in the present investigation, as Tjk was significantly lower in the
COLD condition compared to both CONT and HOT. Though
the experimental hypothesis was proven correct with regard to
COLD, the formulation of the employed protocol (Drust et al.,
2000), as discussed previously, may confound the validity of the
observed data and its interpretation. Unpublished data from our
laboratories suggest that the effects of extreme environmental

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May 2014 | Volume 5 | Article 185 | 7

Taylor et al.

The environment and soccer referee decision mal<ing

conditions on decision making of non-exercising participants
(e.g., goal line officials employed within the UEFA region) causes
a reduction in cognitive performance in a similar COLD condi-
tion, with said performance unaffected in a warmer conditions,
as observed in other previous research (Makinen et al, 2006).
Evidently, the interaction of exercise, cognition and environ-
mental stress is multifaceted, and requires further elucidation,
specifically regarding environments of greater stress than those
used within the present study.

Aside from the environment mediated challenge to cognition
processes, it is possible that cognitive function may be impaired
during by exercise per se (McMorris and Graydon, 1997). Previous
research has found that neural activation associated with a task,
whilst disturbed during task (e.g., exercise), rapidly returns to
baseline levels after exercise (Magnie et al., 2000). Such in-task
disturbance is likely due to a large part of the brain being associ-
ated with basic sensory processes and motor outputs, and thus,
must come at the expense of other neural tasks (Dietrich and
Sparling, 2004). Therefore, future work, utilizing an appropri-
ate protocol as suggested (Williams et al., 2010; Aldous et al.,
2013), should seek to assess decision making ability during the
exercise task itself To enhance ecological validity further the use
of a soccer specific decision making tool should be considered
for future research. The tool used in the present study (PSCHE
Software) was developed for use in a clinical setting. And although
it provides useable, quantitative data it has not been employed
extensively in a sporting context, ft may be that a soccer specific
tool more sensitive than the PSYCHE software would highlight
differences in decision making that were not observed in the
present study.

In conclusion, intermittent sprint exercise in any condition did
not have a significant effect on decision making ability of the
participants. The exercise protocol utilized (Drust et al, 2000),
as described, likely did not provide a truly indicative simula-
tion of the internal and external load of soccer match play, and
thus referee movement patterns. This lack of reflective internal
and external loads resulted in the tripartite relationship between
environmental UEFA region and season specific environmental
stress, cognition processes and exercise not being securely and
fully elucidated within the utilized experimental design. Future
work should look to assess cognition during exercise/game play
in conjunction with the use of an appropriately constructed pro-
tocol (e.g., Aldous et al., 2013) in a variety of environmental
conditions to enhance ecological/external validity to not only the
UEFA region, but that of Federation Internationale de Football
Association (FIFA).

FUNDING

This was a Union of European Football Associations (UEFA)
funded project.

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Conflict of Interest Statement: This original research was funded by the Union of
European Football Associations (UEFA). The authors declare that the research was
conducted in the absence of any commercial or financial relationships that could
be construed as a potential conflict of interest.

Received: 07 February 2014; accepted: 25 April 2014; published online: 20 May 2014.

Citation: Taylor L, Fitch N, Castle P, Watkins S, Aldous J, Sculthorpe N, Midgely A,

Brewer ] and Mauger A (2014) Exposure to hot and cold environmental conditions

does not affect the decision making ability of soccer referees following an intermittent

sprint protocol. Front Physiol. 5:185. doi: 10.3389/fphys.2014.001S5

This article was submitted to Exercise Physiology, a section of the journal Frontiers in

Physiology.

Copyright © 2014 Taylor, Fitch, Castle, Watkins, Aldous, Sculthorpe, Midgely, Brewer
and Mauger. This is an open-access article distributed under the terms of the Creative
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